Ideally, reference values could be established for a tumor marker to differentiate healthy individuals from those known to have cancer. Establishing reference intervals for tumor markers becomes essential if the tumor marker is produced by healthy tissues, or if the marker is produced in small quantities during infections, inflammation, or other benign pathologic conditions. The clinical sensitivity and specificity of a tumor marker's ability to identify cancers are highly dependent upon establishing the reference intervals.

Based on the type of cancer, reference intervals or reference limits may also need to be established for tumor markers based on age and gender.